When you make a call with a SIM that has MEX enabled all calls are sent to the API.
All calls made to your MEX enabled cellphone number are also routed to to the API. As
a reslult all calls are handled buy the voice_start paramter on the number object.
You may use all the functions in the API on all calls.
To forward a the call to phone you need to make a connect action to the phoenumber.
Calls to the MEX phoenumber from the API will be connected to the phone with the SIM inside.